Are you a collector of art?
"A collector of art" is a noun phrase functioning as subjective predicative complement of the verb "are". It's called subjective because it relates to the subject, the noun phrase "you". Internally, the noun phrase has "a" as determiner, and "collector" as head, which has the preposition phrase "of art" functioning as its complement.
The predicate consists of the verb phrase "__ a collector of art", where the gap notation '___' represents the prenuclear predicator "are". It's a prenucleus because it's external to the nucleus clause "you __ a collector of art".